OBJECTIVE: Hepatocyte nuclear factor-4alpha (HNF4A) is a transcription factor that influences plasma triglyceride metabolism via an as of yet unknown mechanism. In this study, we searched for the critical protein that mediates this effect using different human model systems. METHODS AND RESULTS: Up- and downregulation of HNF4A in human hepatoma Huh7 and HepG2 cells was associated with marked changes in the secretion of triglyceride-rich lipoproteins (TRLs). Short interfering RNA (siRNA) inhibition of HNF4A influenced the expression of several genes, including acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1). siRNA knockdown of DGAT1 reduced DGAT1 activity and decreased the secretion of TRLs. No additive effects of combined siRNA inhibition of HNF4A and DGAT1 were found on the secretion of TRLs, whereas the increase in TRL secretion induced by HNF4A overexpression was largely abolished by DGAT1 siRNA inhibition. A putative binding site for HNF4A was defined by in silico and in vitro methods. HNF4A and DGAT1 expressions were analyzed in 80 human liver samples, and significant relationships were observed between HNF4A and DGAT1 mRNA levels (r(2)=0.50, P<0.0001) and between DGAT1 mRNA levels and plasma triglyceride concentration (r(2)=0.09, P<0.01). CONCLUSION: This study identified DGAT1 as an important protein that participates in the effect of HNF4A on hepatic secretion of TRLs.
OBJECTIVE:Hepatocyte nuclear factor-4alpha (HNF4A) is a transcription factor that influences plasma triglyceride metabolism via an as of yet unknown mechanism. In this study, we searched for the critical protein that mediates this effect using different human model systems. METHODS AND RESULTS: Up- and downregulation of HNF4A in humanhepatomaHuh7 and HepG2 cells was associated with marked changes in the secretion of triglyceride-rich lipoproteins (TRLs). Short interfering RNA (siRNA) inhibition of HNF4A influenced the expression of several genes, including acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1). siRNA knockdown of DGAT1 reduced DGAT1 activity and decreased the secretion of TRLs. No additive effects of combined siRNA inhibition of HNF4A and DGAT1 were found on the secretion of TRLs, whereas the increase in TRL secretion induced by HNF4A overexpression was largely abolished by DGAT1 siRNA inhibition. A putative binding site for HNF4A was defined by in silico and in vitro methods. HNF4A and DGAT1 expressions were analyzed in 80 human liver samples, and significant relationships were observed between HNF4A and DGAT1 mRNA levels (r(2)=0.50, P<0.0001) and between DGAT1 mRNA levels and plasma triglyceride concentration (r(2)=0.09, P<0.01). CONCLUSION: This study identified DGAT1 as an important protein that participates in the effect of HNF4A on hepatic secretion of TRLs.
Authors: Hovsep Mahdessian; Apostolos Taxiarchis; Sergej Popov; Angela Silveira; Anders Franco-Cereceda; Anders Hamsten; Per Eriksson; Ferdinand van't Hooft Journal: Proc Natl Acad Sci U S A Date: 2014-06-04 Impact factor: 11.205
Authors: Lina S Correa-Cerro; Yulan Piao; Alexei A Sharov; Akira Nishiyama; Jean S Cadet; Hong Yu; Lioudmila V Sharova; Li Xin; Hien G Hoang; Marshall Thomas; Yong Qian; Dawood B Dudekula; Emily Meyers; Bernard Y Binder; Gregory Mowrer; Uwem Bassey; Dan L Longo; David Schlessinger; Minoru S H Ko Journal: Sci Rep Date: 2011-11-23 Impact factor: 4.379